Nature notes

The house sparrow’s bibs are at their most noticeable now and in summerALAMY

House sparrows have started “singing” over the past couple of weeks, although their untidy chirruping could hardly be called musical. As testosterone levels rise at this time of the year, the males’ bills become darker. Males are more boldly plumaged than females and are easily identified by their grey caps and black bibs. The latter markings are at their most noticeable now and in summer. Research suggests that these bib patches — known as “badges” — are signifiers of social status, and that the more dominant males have more extensive areas of black feathers at throat and chest. House sparrows scrap constantly to establish a hierarchy, and those with the largest badges are the most aggressive. In autumn, when the birds moult, the new feathers are grey-tipped,…